Activity-dependent trafficking of lysosomes to dendritic spines. (A) Representative image of secondary dendrites from dissociated hippocampal neurons (DIV 16) transfected with mCherry and LAMP1-GFP under control conditions or after 200 µM AMPA treatment (2 min). Arrows point to LAMP1-GFP in a dendritic spine. (B–D) Quantification of the percentage of spines that have LAMP1-GFP-labeled lysosomes in the head of a spine (B). Number of spines per micrometer (C) and signal intensity of LAMP1-GFP (D) showed no significant difference between treatments. 830 (control) and 833 (AMPA) dendritic spines were analyzed (n = 41 for control and AMPA) over three independent experiments, *, P < 0.05, unpaired Student’s t test. Experimenter was blinded to condition upon analysis. (E) Representative image of secondary dendrites (DIV16) transfected with mCherry and LAMP1-GFP under control conditions or after 200 µM glycine (10 min), 200 µM glycine (10 min) with 50 µM AP5 (60-min treatment pretreatment), or 50 µM AP5 alone (60 min) in HBS containing 0 mM Mg⁺². Arrows point to LAMP1-GFP in a dendritic spine. (F–H) Quantification of the percentage of spines that have LAMP1-GFP-labeled lysosomes in the head of a spine (F). Number of spines per micrometer (G) Signal intensity of LAMP1-GFP (H) showed no significant difference between treatments. 211 dendritic spines for control, 246 for glycine, 356 for glycine/AP5, and 573 for AP5 were analyzed (n = 14 for control, 14 for glycine, 18 for glycine/AP5, and 28 for AP5) over three independent experiments. ***, P < 0.001; **, P < 0.01; *, P < 0.05, one-way analysis of variance with Tukey’s post hoc analysis. Experimenter was blinded to condition upon analysis. All data represent mean ± SEM.